add missing const

If you want to declare a pointer which the address pointed to is constant,
you should declare it as like `static const char *const var = "...";`.

This commit supplies missing `const` and prevents some programming
error in the future.

src/pray.c

@@ -41,9 +41,9 @@ static boolean blocked_boulder(int, int);
  *      responsible for the theft of the Amulet from Marduk, the Creator.
  *      Moloch is unaligned.
  */
-static const char *Moloch = "Moloch";
+static const char *const Moloch = "Moloch";
 
-static const char *godvoices[] = {
+static const char *const godvoices[] = {
     "booms out", "thunders", "rings out", "booms",
 };
 
@@ -2188,7 +2188,7 @@ align_gname(aligntyp alignment)
     return gnam;
 }
 
-static const char *hallu_gods[] = {
+static const char *const hallu_gods[] = {
     "the Flying Spaghetti Monster", /* Church of the FSM */
     "Eris",                         /* Discordianism */
     "the Martians",                 /* every science fiction ever */